Prepare the Crust Dough
In a food processor, pulse the flour, confectioners sugar, and salt. Add the cold butter and pulse until the mixture resembles coarse crumbs. In a small bowl, whisk the egg yolks and water, then stream this into the processor, stopping just as the dough forms a ball. Form the dough into a disk, wrap it in plastic, and chill for at least 30 minutes.

Form the Mini Shells
Preheat your oven to 350°F (175°C). On a floured surface, roll the chilled dough to ⅛-inch thickness. Use a 3-inch round cutter to cut out circles and gently press them into a mini muffin tin. Freeze the tray for 10 minutes to help prevent the crusts from shrinking during baking.

Mix the Filling
In a saucepan over low heat, melt the butter. Remove the pan from the heat and stir in the chopped chocolate until it is completely melted and smooth. In a separate bowl, whisk together the corn syrup, eggs, brown sugar, cocoa powder, salt, and vanilla. Slowly whisk in the warm chocolate mixture until combined, then stir in the chopped pecans.

Assemble and Bake
Spoon the filling into the chilled, unbaked shells, filling them about three-quarters full to avoid spillage. Bake for 20-25 minutes, or until the crust is golden and the center has a slight jiggle.

Cool Before Serving
Allow the mini pies to cool in the muffin tin for 15-20 minutes. This is a crucial step that allows the filling to set properly. After they have firmed up slightly, carefully transfer them to a wire rack to cool completely.